Natural products are regaining their traditional importance as drug candidates, leads for drug candidates and biological probes. Complex natural products typically contain many stereocenters, but only one or at most a handful of stereoisomers are available for study. A new and general approach to making natural product stereoisomer libraries is being developed. The libraries are made as mixtures coded with fluorous (fluoroalkyl) tags, which allows for isolation of individual pure products at the final stage. The total synthesis of 16 isomers of murisolin in a single mixture library by using four fluorous tags and four members of a new class of tags will be accomplished. This new "double tagging" method will be considerably more efficient than the current single tagging method, which requires four separate mixtures to be made to produce sixteen compounds. The stereoisomer library members will be tested for their anticancer activity, and this will provide the first detailed stereostructure/activity relationship for any acetogenin. The total synthesis of all 64 isomers of the protein phosphatase inhibitor cytostatin will be undertaken by using a combination-of double tagging and splitting. Once the sixty-four member library of individual cytostatin isomers is in hand, the stereostructure of cytostatin will be assigned, and the samples will be tested as potential selective phosphatase inhibitors. A new iterative, multi-tagging strategy for synthesis of natural products with repeating stereocenter units such as polyols will be reduced to practice. To prove the concept, first eight diastereomers and later all sixteen isomers of passifloricin A will be synthesized. [unreadable] [unreadable]